In an uplink system which uses Single Carrier Frequency Division Multiplexing Access (SC-FDMA) technologies, information is generally transmitted through the following procedure. FIG. 1 illustrates an example block diagram illustrating SC-FDMA information transmission. As shown in FIG. 1, a serial information sequence for transmission is converted into a parallel sequence and Discrete Fourier Transform (DFT) is then performed on the parallel sequence. Then, Inverse Fast Fourier Transform (IFFT) is performed on the DFTed data. Here, the size of information inserted into IFFT indices need not be equal to the size of the IFFT index and the DFT result must be mapped to sequential IFFT input indices to be transmitted. A parallel sequence of values obtained through IFFT is then converted back to a serial sequence. A Cyclic Prefix (CP) is then added to the serial sequence to create a signal having an Orthogonal Frequency Division Multiplexing (OFDM) symbol structure. The created signal is then transmitted through an actual time/space medium.
In the case where DFT-precoded information is inserted into IFFT indices in an OFDM fashion, it is necessary to insert the information into sequential IFFT indices in order to achieve a low Peak to Average Power Ratio (PAPR) and a low Cubic Metric (CM) while maintaining single carrier characteristics. That is, it is necessary to insert the DFT-precoded information into sequential OFDM subcarriers. Therefore, when information is transmitted in uplink, even multiple types of information having different characteristics (for example, control information and data information) are multiplexed together and the multiplexed information is then transmitted in an OFDM fashion after DFT precoding. The term “data information” or “data” used in the present invention refers to data other than control information such as video or audio data.
FIG. 2 is a block diagram illustrating a procedure for processing an uplink transmission channel. As shown in FIG. 2, data information is segmented into a number of code blocks according to the size of a transport block for uplink transmission. A Cyclic Redundancy Check (CRC) code is then attached to each of the code blocks. Then, the code blocks are subjected to channel coding and rate matching processes and are then concatenated to create a single data information sequence. The data information sequence is multiplexed with the control information.
Control information that can be transmitted together with data in uplink is classified into two types. Specifically, such control information can be classified into Acknowledgement (ACK)/Negative Acknowledgement (NACK) information, which is information for confirmation of the receipt of downlink data, and other types of control information. A terminal or User Equipment (UE) transmits the ACK/NACK signal for the downlink data only when downlink data is present. A UE, which does not know if it will receive downlink data, transmits the two types of control information together with data in uplink while discriminating between the two types of control information since the UE may not know that it should transmit uplink ACK/NACK information even though it should transmit the uplink ACK/NACK information. Therefore, all instances of the terms “control information” described in the present invention refer to control information other than ACK/NACK information and the ACK/NACK information will be separately described.
When data is transmitted in uplink, the data can be transmitted together with control information or can be transmitted together with both control information and ACK/NACK information. Data may also be transmitted together with ACK/NACK information only. A transmission information sequence created by multiplexing data with control information or ACK/NACK information is transmitted using an SC-FDMA scheme.
All information that a terminal or User Equipment (UE) transmits in uplink is controlled by a base station or eNode B (eNB). When a UE has received data in downlink, the UE transmits ACK/NACK information in uplink in order to notify the eNB of whether or not the data has been successfully received. A Channel Quality Indicator (CQI) can be used to control data transfer rate. Using the CQI, the eNB can transmit data through a band providing a good channel quality response, thereby improving system performance. That is, the CQI is information that is fed back in uplink for transmission of downlink data. Therefore, the ACK/NACK information or the CQI can be considered information that is not associated with uplink data transmission but is associated with downlink data transmission.
On the other hand, a Scheduling Request (SR) is information that the UE transmits in uplink when new data for uplink transmission is created at a transmission buffer queue in the UE. When the eNB has received an SR from the UE, the eNB transmits control information in downlink to allow the UE to transmit the data. Therefore, the SR is information that is associated with uplink data transmission.
When the data, CQI, SR, and ACK/NACK information described above are transmitted in uplink, there is a problem of how to combine the data, CQI, SR, and ACK/NACK information for transmission.